Sensors based on the Hall-effect, referred to as Hall sensors, are widely used as magnetic field sensors. A Hall sensor includes one or more Hall-effect sensing elements that measure magnetic field strength and/or direction. These measurements are used to obtain parameters, such as distance, position, and rotational speed. However, Hall sensing elements exhibit offsets at their outputs due to mechanical stresses, doping, and geometrical errors. Also, Hall sensing elements exhibit offset drift, which results in an unpredictable and time-varying output error.
Offsets in Hall sensing elements can be reduced via the spinning current method, where the bias current of a Hall sensing element is spatially rotated around the Hall sensing element, while the output is averaged in time. This reduces offset and offset drift. Also, Hall sensor offset can be instantaneously reduced by orthogonally coupling two or more Hall sensing elements.
Input amplifiers receive and amplify the signals from the Hall sensing elements. These input amplifiers include noise and amplifier offsets. Dynamic offset-cancellation techniques, including auto zeroing and chopping techniques, can be used to reduce the noise and offset of the input amplifiers. However, these techniques produce residual offsets caused by demodulated switching peaks and/or imperfections in the amplifier circuit.
For these and other reasons there is a need for the present invention.